Pneumatic shell structures constructed from synthetic resin films

ABSTRACT

Disclosed herein is a pneumatic shell structure which is constructed from two sheet layers, each composed of a plurality of long rectangular synthetic resin films which are arranged side by side in a manner that longitudinal side edge portions of the films are mutually superimposed. The sheet layers are hermetically sealed about their edges to a support frame, so that the arranged films can uniformly carry the stress created on the sheet layers owing to the inner pressure of the airtight air chamber.

United States Patent Ikaiet a1.

[54] PNEUMATIC SHELL STRUCTURES CONSTRUCTED FROM SYNTHETIC RESIN FILMS[72] Inventors: Masai-u Ikai, Kyoto-shi; Toshikazu Ishii,

Otsu-shi; Michiaki Higashikuze, Takatsuki-shi, all of Japan [73]Assignee: Toray Industries, Inc., Tokyo, Japan [22] Filed: July 18, 1969[21] Appl. No.: 843,068

[30] Foreign Application Priority Data July 25, 1968 Japan ..43/52711Aug. 1, 1968 Japan.... ....43/54264 Dec. 26, 1968 Japan... ....43/951102,398,886 4/1946 Drake et a1.

[451 May 23, 1972 2,425,060 8/ 1947 Gildehaus ..52/ 200 3,122,985 3/1964Osborne ..52/2 3,127,699 4/1964 Wasserman... 52/200 X 3,176,982 4/1965ODaniell... ..52/2 X 3,298,142 l/1967 Isaac ..52/2 3,307,309 3/ l 967Bloxsom ..52/200 3,444,033 5/1969 King 161/39 X 3,455,073 7/ 1969Kiekhaefer ..52/ 200 3,481,087 12/1969 Stafford ..52/2 2,610,936 9/1952Carlson... 161/109 X 3,300,927 1/ 1967 Bettoli ..52/622 X 3,421,9771/1969 Hutchinson et a1 ..52/622 X FOREIGN PATENTS OR APPLICATIONS1,273,271 8/1961 France ..52/200 Primary Examiner-Price O. Faw, Jr.Attorney-Robert E. Burns and Emmanuel J. Lobato 57 ABSTRACT Disclosedherein is a pneumatic shell structure which is constructed from twosheet layers, each composed of a plurality of long rectangular syntheticresin films which are arranged side by side in a manner thatlongitudinal side edge portions of the films are mutually superimposed.The sheet layers are hermetically sealed about their edges to a supportframe, so that the arranged films can uniformly carry the stress createdon the sheet layers owing to the inner pressure of the airtight airchamber.

19 Claims, 3 1 Drawing Figures Patented May 23, 1972 3,664,069

8 Sheets-Sheet .1

2 ,1 wil Pa tented May 23, 1972 8 Sheets-Sheet 2 Patented May 23, 19723,664,069

8 Sheets-Sheet 5 Patented May 23, 1972 3,664,069

8 Sheets-Sheet 4.

Patented May 23, 197 2 8 Sheets-Sheet 5 Patented May 23, 1972 3,664,069

8 Sheets-Sheet 6 55 H 64 Hg /4 Patented May 23, 1972 3,664,069

8 Sheets-Sheet 7 TENSION FORCE (kg L Patented May 23, 1972 8Sheets-Sheet a PNEUMATIC SHELL STRUCTURES CONSTRUCTED FROM SYNTHETICRESIN FILMS The present invention relates to pneumatic shell structuresconstructed from synthetic resin films and a method for constructing thesame.

It is well-known that such component structures for buildings such astents, roofs or walls can be made of sheets of synthetic resins such aspolyethylene terephthalate, polyacrylonitrile, polystylene,polyethylene, polypropylene, polyamide or polyvinylchloride, or wovenfabrics, knitted fabrics, non-woven fabrics or nets coated with suchcoating synthetic resins as polyvinylchloride, chlorosulfonatedpolyethylene, chloroprene rubber, butyl rubber or polyurethane.

It is also a kind of known art to construct shell structures utilizingairtight chambers formed by supplying air in between two or moreairtight sheets. These types of structures are generally calledpneumatic shell structures. This pneumatic shell structure can maintainits shape by retaining the stress created in the sheets forming theairtight chamber in a balanced relationship to the internal pressure ofthe gas contained in that airtight chamber. In the construction of suchpneumatic shell structures, a woven fabric coated with such soft highpolymeric compounds as vinyl chloride, chlorinated polyethylene orchlorinated rubber is mainly and conventionally used as a materialsheet. In some cases, such a coated fabric may be further superimposedby other layers of net-like configuration.

On the other hand, also known is the forming of a balloon using mutuallyand suitably bonded films of synthetic resin such as polyethyleneterephthalate. In this case, the balloon forming films are covered withone or more layers of net configuration and the stress created in thefilm is absorbed by the film covering net configuration.

In any of the above-illustrated prior arts, the sheet for forming theairtight chamber is prepared from a three-dimensionally bound filmslayer, by which the sheet is prevented from breaking due to the stresscreated in the sheet. In order to construct a structure of this natureand configuration, it was necessary to cut, sew and bind the componentfilms in he three-dimensional shape. However, because suchthreedimensional preparation required very highly skilled techniques,there has been little penetration of pneumatic shell structures of thistype, particularly large pneumatic shell structure, into actualutilization. Besides the conventional pneumatic shell structures of thistype are fundamentally composed from a pair of sheets disposed in aface-to-face relationship. There was a limitation to the scale of thestructure owing to a limitation to the strength of the component sheets.

Further, in the conventional pneumatic shell structure, peripheral inneredge portions of the sheets which constructs the structure have to befixedly bound using metal fasteners for obtaining an airtight internalcondition of the structure. The metal fasteners of this kind are apt torust by contact with water such as rain and it causes undesirableleakage of water into the structure through the rusted portions. Suchwater is frozen by the lowering of the surrounding temperature,especially in winter season, to form a bar in uniform distribution ofthe stress created in the sheets or to contaminate the films surface.

When the inner edge portions of the sheets are bound together using suchfastening devices, such as fastening bolts, the difference in elasticmodulus, thermal expansion coefficient or creep property against anexternal force between the sheet and the fastening device often causesundesirable concentration of a shearing force upon the fastened portionresulting in accidental breakage of those portions.

In case the constructed pneumatic shell structure is provided withcorner portions, water is liable to get into the structure through thecomer portions and a considerably complicated and highly skilledtechnique is required for preventing such undesirable water leakage.

Still other drawbacks of the pneumatic shell structure of theconventional type is found in the fact that the component sheets are notso durable against exposure to sun-light.

A principal object of the present invention is to provide a pneumaticshell structure of relatively simple construction wherein stress causedby the pressure of the internal gas can be distributed uniformly in thesheets composing the structure and a method for constructing such astructure in a relatively simple manner.

Another object of the present invention is to provide a pneumatic shellstructure wherein water leakage through peripheral inner edge portionsof the component sheets is completely prevented.

Still another object of the present invention is to provide a pneumaticshell structure having corner portions resistant against water leakagetherethrough.

A further object of the present invention is to provide a pneumaticshell structure durable against attack by sun-light and other weatherconditions.

In order to attain the above-described several objects, the pneumaticshell structure of the present invention comprises a pair of sheetlayers, an upper sheet layer and a lower sheet layer, arranged in aface-to-face relationship and forming an airtight chamber therebetween.Each of the upper and lower layers comprises an airtight inside layerforming the airtight chamber, an outside layer facing outside, and oneor more intermediate layers inserted between the airtight inner layerand the outside layer for carrying most of the stress created on thesheet layer. This intermediate layer is prepared from a plurality ofsynthetic resin films having a relatively long rectangular profile, inother words, a belt-like shape, and smooth surfaces. The longrectangular films are arranged in a side-by-side relationship in whichlong side edge portions of adjacent films are superimposed to each otherwithout adhesion.

The thickness of the film usable for composing the shell structure ofthe present invention should preferably be 0.5 mm or thinner and theinitial tensile elasticity should be at least 4 X [0 kglcm or morefavorably be at least 2 X 10 kglcm Films made of polyethyleneterephthalate, polyethylene, polypropylene, polyvinyl chloride,polycarbonate or ethylenevinylacetate copolymer can be advantageouslyused for the purpose of the present invention. Among the abovedescribedpolymers, polyethylene terephthalate or hard polyvinyl chloride are usedwith best results. Such synthetic I resin films may be sputtered withaluminum or copper layer on at least one of their surfaces in a mannerof vacuum evaporation.

Dimensions and shape of the film are to be selected suitably inaccordance with the dimensions and shape of the shell structure to beconstructed. Generally for the practical utilization of the act of thepresent invention, a long belt-like film which is wound into a roll-formis suitable. The relationship between the unit length and unit width ofsuch a belt-like film is dependent upon the desired curvature of thepneumatic shell structure. Practically, in case the tangent, or rise, ofthe structures curvature is one-tenth, the films width should preferablybe in a range from one-tenth to one-fifth of the film's length.

Construction of the shell structure from the component films is carriedout by forming respective layers on a mold table having a curved surfacecorresponding to the desired curvature of the pneumatic shell structure.For example, in constructing the upper sheet layer of the shellstructure, an inside layer is firstly formed on the curved mold table.This inside layer may be composed of either a single film sheet or asheet composed of a plurality of belt-like films airtightly adhered orsealed to each other at their contacting side edge portions by asuitable adhesive, adhering tape or grease. Secondly, a needed number ofsynthetic resin films are arranged on the airtight inside layer in aparallel arrangement in which their side edges are superimposed mutuallybut not adhered. Thus arranged films form an intermediate layer forcarrying most of the stress created in the shell structure sheet. Incase two or more of the arranged film layers are piled up forconstructing an intermediate layer, each arranged films layer issuperimposed on another in a manner in which the longitudinal directionof the films in the respective layers should be in a perpendicularlycrossed condition.

Thirdly, after the completion of the arrangement of the intermediatelayer or layers, the outside layer is formed thereon. This outside layermay be composed of either a single film airtight sheet or a sheetcomposed of a plurality of belt-like films superimposed on each other attheir side inner edge portions, and, if desired, adhered airtightly thesuperimposed portions by a suitable adhesive or adhering tape. In orderto protect the shell structure sheet layer from undesirable influencesof sunlight, the outside layer may be composed of synthetic resin filmssubjected to a suitable treatment for bestowing ultraviolet rayabsorption property or heat reflection property.

Further features and advantages of the present invention will beapparent from the ensuing description, reference being made to theaccompanying drawings showing preferred embodiments wherein;

FIG. 1A is a plan view of a model of the pneumatic shell structure ofthe present invention;

FIG. 1B is a cross section taken along a line BB in FIG. 1A;

FIG. 1C is a side cross sectional view for showing a layered arrangementof films composing the pneumatic shell structure shown in FIG. 1A;

FIG. 2A is a perspective representation of a reinforcement usable forthe pneumatic shell structure of the present inventron;

FIG. 2B is a side cross section of the reinforcement shown in FIG. 2A;

FIG. 2C is an explanatory drawing for showing a reinforcing mechanism ofthe reinforcement shown in FIG. 2A;

FIG. 3A is a cross sectional representation for showing the attachmentof the reinforcement shown in FIG. 2A onto an inside wall surface of anairtight chamber of pneumatic shell structure of the present invention;

FIG. 3B is an explanatory side view of the inflated pneumatic shellstructure of the present invention provided with the reinforcement shownin FIG. 2A;

FIG. 4A is a cross section of a model of the pneumatic shell structurecomposed of a plurality of film layers;

FIG. 4B is a graphical diagram showing a pressure distribution in theshell structure as shown in FIG. 4A;

FIG. 5A is a cross section of a model of the pneumatic shell structurecontaining an air layer between the film layers;

FIG. 5B is a graphical diagram showing a pressure distribution in thepneumatic shell structure as shown in FIG. 5A;

FIGS. 6 and 7 are cross sectional representations of some examples of aventilating means usable in combination with the pneumatic shellstructure of the present invention, respectivcly;

FIGS. 8 and 9 are cross sectional side views of some examples of theconventional devices for fastening the peripheral edge portion of thesheet layer of the pneumatic shell structure onto a supporting member;

FIGS. 10 to 17 are cross sectional side views of several embodiments ofsealing means usable for the pneumatic shell structure of the presentinvention;

FIG. 18 is a graphical diagram for showing a covering effect of ametallic surface of the supporting member with various covering paintlayer according to the present invention;

FIG. 19 is an explanatory drawing for showing comer parts of thepneumatic shell structure of the present invention,

FIG. 20 is a perspective view of the comer part of the pneumatic shellstructure of the present invention having a cut-off;

FIG. 21A is an enlarged perspective view of the cut-off corner part ofthe pneumatic shell structure;

FIG. 21B is a perspective view of a corner sealing member adapted forbeing attached to the cut-ofi corner shown in FIG. 21A;

FIGS. 21C and 21D show a manner of fixing the comer sealing member shownin FIG. 218 to the cut-off comer part;

Referring to FIG. 1A, a model configuration of the pneumatic shellstructure of the present invention is illustrated. As shown in thedrawing, the shell structure 1 comprises a layered sheet part 2 and afastener part 3 for providing a seal around the edges of the sheet part2. As is shown in FIG. 1B, the sheet part 2 comprises an upper sheetlayer 4, a lower sheet layer 5, and an airtight chamber 6 disposedbetween the two layers 4 and 5. The fastener part 3 seals the peripheraledge portion of the layers 4 and 5 together into an airtight condition.Upon supplying air into the airtight chamber 6 formed in between thetightly connected layers 4 and 5, both layers 4 and 5 are inflatedoutwardly in an arc form, by which the shell structure I having curvedsurfaces is formed. The configuration of the sheets layers 4 and 5 isshown in FIG. 1C, wherein the upper sheet layer 4 comprises severalcomponent layers including an outside layer 7a; intermediate layers 8a,8b and 8c and 9a and 9b and an inside layer 10a, arranged in asuperimposed condition. In the case of the lower sheet layer 5, thecomponent layers are superimposed also, but in reverse order and includeonly three intermediate layers 84', 8e and 9c, enclosed by an innerlayer 10b and an outer layer 7b.

As is shown in the drawings, each component layer comprises a pluralityof strips of synthetic resin films arranged in a manner in which thefilms are disposed in a substantially parallel condition, and in whicheach strip is shifted transversely in the same direction from thepreceding strip so that the longitudinal side edges of one strip overlapthe said edges of each preceding and succeeding strip.

When the longitudinal direction of the films in a componental layer, forexample layer in FIG. 1C, is laid in the X direction in FIG. 1A, thelongitudinal directions of the films in the adjacent component layers,for example layers 7a and 9a are laid in the Y direction which crossesperpendicularly with the X direction.

That is, in FIG. 1C, the films in the outer layer 7a run in the Ydirection, the films in the intermediate component layers 80, 8b and 80run in the X direction, the films in the intermediate component layers9a and 9b run in the Y direction, and the films in the inside layer 10arun in the Y direction. In such a construction, the overlapping portions1 l of the films in the outer layer 70 are hermetically fixed togetherby a suitable fixing means such as an adhesive or adhering tape forpreventing the shell structure from penetration of water. However, wherethe shell structure 1 is intended only for indoor use, the overlappingportions in the outer layer 7a do not always require such fixing. Theoverlapping portions of films in the inside layer 10a, however, must behermetically sealed together by a suitable adhesive, adhering tape orgrease for maintaining the inner chamber 6 in an airtight condition forboth indoor and outdoor use. The overlapping portions of films in thecomponental layers 8a, 8b, 80, 9a and 9b of the intermediate layer arenot fixed.

When air is supplied into the airtight chamber 6 of the shell structure1 of the above-described configuration, the internal pressure caused bythe filled air balances itself with stress created in the sheet layersand the created stress is uniformly distributed in the films composingthe sheet layers. Because the films composing the intermediate componentlayers are not adhered to each other as described above, they canperform a suitable relative displacement in accordance with the internalpressure of the air resulting in a formation of a smooth curvature.Owing to this free relative displacement of the component films most ofthe stress caused by the internal pressure applied to the sheet layerscan be distributed uniformly in the intermediate components layers.

By employing the above-described art of the present invention, anydesired curvature can be obtained from flat films in a simple manner andsome of the adhering operations can be omitted resulting in aconsiderable simplification in the pneumatic shell structureconstruction.

In order to retain the shape of the pneumatic shell structure thusconstructed, reinforcing means are further proposed in the art of thepresent invention as is hereinafter disclosed.

Referring to FIGS. 2A, 2B and 2C, an embodiment of such reinforcingmeans is shown. In the shown embodiment, a reinforcement l3, composed ofan elastic synthetic resin film, includes a bonding surface 14 and areinforcing body 16 connected to the bonding surface 14 at a bent edgein a bendable relationship. The bonding surface 14 is adapted forattachment to an inside wall surface of the airtight chamber 6 as shownin FIG. 3A, and under this condition, when the air is filled into theairtight chamber 6 and the sheet layers are expanded toward the outsideand provided with curvatures of a desired nature, the bonding surface 14is expanded and converted into a curved surface 140 following thecurvature formation of the sheet layers and the bent edge 15 is alsostretched and converted into a curved edge 15a as shown with a dottedline in FIG. 2C. With this stretch of the bent edge 15 into the curvededge 15a, the reinforcing body 16 is paced into a bent relationship tothe curved surface 14a approximately with a right angle as shown by adotted line and designated with a reference numeral 16a in FIG. 2C.Then, as is shown in FIG. 3B, the reinforcing body 16 now in the 160position extends from one sheet layer to another through the airtightchamber 6 so as to support the two layers in a given configurationalrelationship. Further reinforcing effect can be obtained if tworeinforcements 13 are disposed in a closely contacting arrangement asshown in FIG. 3B. For easy movement of the reinforcing body 16 ofreinforcement 13, one or more apertures may be formed through thereinforcing body 16.

For better shape retention of the shell structure in an inflatedcondition, the present invention is further provided with the followingimprovement. In the shell structure configurational mechanism of thepresent invention, each sheet layer is composed of a plurality oflayered films, the internal pressure caused by the air supplied into theairtight chamber is absorbed by the componental films by which the shapeof the shell structure is retained as desired.

For example, if a sheet layer is composed of four film layers 21 to 24superimposed mutually in close contact as shown in FIG. 4A, an internalpressure a of the airtight chamber 6 is uniformly distributed into thefour film layers and absorbed therein as shown in FIG. 4B. In case anair layer exists between the film layers 23 and 24, as shown in FIG. 5A,the film layers 21 to 23 absorbs only a part c of the pressure a and thefilm layer 24 should be for absorbing the remaining part b (b =a c) asshown in FIG. 5B. That is, the stress caused by the internal pressure isdistributed non-uniformly into the componental layers composing thesheet layer. In order to eliminate this non-uniformity in the stressdistribution, it is necessary to discharge the air contained within thespace of the sheet layer so as to obtain a closely contactingarrangement of the componental layers composing the sheet layer. In thisconnection, however, the pneumatic shell structure of the presentinvention is advantageous in the configuration of the sheet layerwherein, only the inside layer is hermetically formed and the remainingoutside and intermediate layers are respectively composed of belt-likefilms superimposed mutually at their side edge portion without anyadhering, that is, the remaining layers are formed as air permeable.But, when the shell structure is purposed for use out-doors, the outsidelayers should be hermetically formed so as to prevent unfavorableseepage of water and/or fine particles of dust. In this case, the shellstructure needs a particular means for ventilating the air containedwithin the sheet layer part.

Some examples of such a ventilating means are illustrated in FIGS. 6 and7. In the example shown in FIG. 6, a superimposed portion 26 of theoutside layer 24 is provided with an air pipe 27 having an outlet 29directed downwards. In the example shown in FIG. 7, the fastened portionof the sheet layer is also provided with an air pipe 27 inserted inbetween the outside layer 24 and the intermediate layer 23. This airpipe 27 is provided with a valve 28 for preventing counterflow as shownin FIG. 6. So, only air contained inside can be discharged into theatmosphere therethrough, but external water or air can not get insidepassing therethrough. By completely discharging air contained within thesheet layers utilizing the abovedescribed ventilating means, all thecomponental film layers composing the sheet layer can be brought into acomplete contact and the stress caused by the internal pressure can bedistributed uniformly into respective componental film layers.

Peripheral edge portions of the pneumatic shell structure must be sealedto affect watertightness using suitable metallic fastening devices. Itis well-known that water tends to get inside the sheet layer passingthrough the fastened portions and thus invaded water causes rusting ofthe metallic fastening devices. Further, the invaded water has atendency to become frozen by the lowering of the surrounding temperatureresulting in non-uniform distribution of stress respective componentalflm layers. In order to eliminate this troublesome water invasion, theart of the present invention includes provision of novel sealing meansusable for the pneumatic shell structure.

Referring to FIGS. 8 and 9, some examples of the fastening device of theconventional type are shown. In the example shown in FIG. 8, the edgeportions of the upper sheet layer 4 and the lower sheet layer 5 issandwiched by a supporting member 31 and a fastening member 32 andwatertightly sealed by a fastening bolt 33. However, in thisconstruction, outside water can easily get inside the sealed partfollowing along the surface of the fastening bolt 33, and the crevicesspaced between the fastening member and the sheet layer. In the exampleshown in FIG. 9, the edge portion of the sheet layers is curved alongthe peripheral surface of the supporting member 31a and is fastened bythe fastening bolt 33 plated to the supporting member 31a beingsandwiched by the supporting member 31a and a fastening member 32a. Alsoin this case, outside water gets inside following along the surface ofthe fastening bolt 33 and the crevices spaced between the fasteningmember 32a and the sheet layer. Several methods for overcoming theabovedescribed drawbacks possessed by the conventional fastening deviceare shown in FIGS. 10 to 17.

In the embodiment shown in FIG. 10, a bottom member 35 of the sealingmeans is disposed to the supporting member 31a in a manner shown in thedrawing. An end 38 of a top member 37 of the sealing means iswatertightly adhered by a adhesive layer 41 to an outside surface of thesheet layer 2; where as another end 39 of the top member is watertightlyfixed by a fixing member 40 to one end 36 of the bottom member 35. Anadditional film 42 is disposed covering the adhered end 38 of the topmember 37 for a further complete sealing effect. If the sheet layer 2performs slight displacements upon receipt of x or y-directionaltension, the top member 37 can follow the displacement easily. Thus, themetallic fastening bolt 33 can be completely protected by the bottommember 35 and the top member 37. The top member is made of a watertightsheet such as synthetic resin film.

In case of the embodiment shown in FIG. 11, a covering member 43 coversthe fastening bolt 33, fastening nut 34 and the fastening member 32a andboth ends 44 and 45 of the covering member 43 adhere to the outsidesurface of the sheet layer 2 and the supporting member 31a,respectively, by waterproof layers 46 of an adhesive such as siliconeresin adhesive. One end 38 of the top member 37 watertightly adheres tothe outside surface of the sheet layer 2 by a suitable adhesive layerand also the other end 39 thereof is watertightly fixed to one end 36aof the supporting member 31a by the fixing member 40. The coveringmember 43 is made of a synthetic resinous material. By employing theabovedescribed sealing means, the fastened part of the shell structurecan be completely protected from invasion by water.

In the embodiments shown in FIGS. 12 and 13, the fastening member 32 isprovided with a recess 49 formed in an upper end 52 thereof. This end 52is also provided with an annular recess 50 encircling the fastening bolt33. The recess 49 is filled with suitable packings 47a. A covering plate51 is connected to a lower end 53 of the fastening member 32 extendingtowards the supporting member 31 and a packing 47c is inserted inbetween the end of the sheet layer 2 and the covering plate 51. Theannular recess 50 is provided with an annular packing 47b of an elasticnature, the inside peripheral surface of the annular packing 47b is putin close contact with the periphery of the fastening bolt 33 and theoutside peripheral surface thereof is in close contact with the annularrecess 50. Suitably selected elastic material may be used for theannular packing 47b in conformity to the requirement of the end use.

Referring to FIGS. 14 and 15, an embodiment of the sealing meansincludes an encircling member 54 disposed on the fastening member 32 andencircling the fastening bolt 33 and the nut 34 and a suitable sealingmaterial 55 is filled inside the encircling member 54. Elastic sealantsand oil coating materials are useful for this purpose. By disposing sucha sealing member, invasion of water into the membraneous layer structurefollowing the fastening bolt can be completely obviated.

FIG. 16 shows another embodiment of the sealing means including asuitable sealing paint layer 55a painted covering the fastening meansand the sealing means. The sealing paint can be selected from acrylicpolymer resin, polyvinyl chloride resin, polyurethane resin and epoxyresin paints according to the requirement in the end use.

The embodiment shown in FIG. 17 comprises two recesses 49 and 56 formedin the upper and lower ends 52 and 53 of the fastening member 32.Together with these, an annular recess 50 is also formed encircling thefastening bolt 33. In combination with this mechanical construction, thesupporting member 31 is provided with a recess 56a formed in one end 57thereof and an annular recess 50a encircling the fastening bolt 33. Asis shown in the drawing, the recess 49 is provided with an elasticpacking 58 inserted watertightly therein and the recesses 56 and 56areceive respective ends of a packing 59 for covering the end of thesheet layer 2. Elastic packings 60 and 61 are inserted into the recess50 of the fastening member 32 and the recess 50a of the supportingmember 31. Any kind of elastic packing material selected from polyvinylchloride resin, polyolefine resin, rubber packing, etc., can be used forthis purpose in accordance with the requirement of the end use. Thesealing means of the above-described type can prevent the accidentalseepage of water into the shell structure.

The art of the present invention is provided with a means for protectingthe sheet layers fastened between the metallic supporting member and themetallic fastening member. Comparing the physical properties of thesynthetic resin film for composing the sheet layer of the presentinvention with these of metallic material of the supporting member orthe fastening member, the former has a smaller elasticity, largerthermal expansion and larger creepness than these of the latter,respectively. Thus, in case the sheet layer immediately contacted themetallic supporting member or the metallic fastening member, there was abreaking of the sheet layer due to concentration of stress. It was foundthat such disadvantages can be overcome by insertion of packing sheetshaving a tensile elasticity of at least 20,000 kglcm respectively,between the metallic supporting member and the sheet layer, and/or themetallic fastening member and the sheet layer. Packing sheet having atensile elasticity smaller than 20,000 kg/cm such as vulcanized rubbersheet, foamed polyurethane sheet impregnating with asphalt, and softpolyvinyl chloride sheet has a tendency of deformation by tensile stressdue to fastening action, thus, it is difficult that the sheet layer isalways uniformly fastened by the above-mentioned low elasticity packingsheet. As the packing sheet for the fastening means, according to thepresent invention is useful, a packing sheet having a tensile elasticityof at least 20,000 kg/cm such as phenol resin, melamine resin, siliconresin, polyester resin, epoxy resin, styrol resin, styren-acrylonitrilecopolymer resin, polymethyl methacrylate resin, polyolefine resin,polyamide resin, polycarbonate resin sheet.

Reinforced packing sheets which contains reinforcing fiber such as fiberglass may be used advantageously for the purpose mentioned above.

The edge portions, in other words, the peripheral end portions, of thesheet layer is maintained in a present shape by a metallic supportingmember. In order to prevent the occurrence of metal rusting and torealize a uniform transmission of the stress from the sheet layer to themetallic supporting member by increasing a frictional force between thetwo, it is desirable to cover the metallic surface with a paint layerhaving a pencil hardness of degree F or higher and Sward Riickershardness value, of at leastZS. apaint forpresent- TABLE 1.-HARDNESS 0FPAINT MEMBRANE Sword Pencil Riicker's Hardness hardness hardness Paintmembrane:

A, 011 paint--- B 25 B, epoxy esterz- H 30 Sixteen sheets ofpolyethylene terephthalate films of 250 thickness, 88 cm width and 30 cmlength were superimposed together. Both terminations of mm length of thesuperimposed films were gripped between the two steel plates andfastened with a bolt passing through holes formed through the middleportion of the steel plates. The fastening force was of 5.95 tons/singlebolt when measured by a torque meter and converted into a correspondingshaft force. Thus prepared specimen was subjected to tensile elongatingat an elongation rate of 5 mm/min on a tensile tester (type IS 5,000which is obtained from Shimazu Seisakusho, Japan), the relation betweenthe tensile force and the displacement of the gripped termination of thesuperimposed film sheets was observed and the result is shown in FIG.18. In the drawing, the curve A is for the oil paint membrane case, thecurve B for the epoxy ester membrane case and the curve C is for nopaint case. It is apparent from this shown result that the terminationdisplace ment is minimum in case the epoxide ester layer is formed. Thismeans that the frictional force in between the painted steel surface andthe film surface is considerably large in case of this specimen.

Next, a method for preventing water seeping into the pneumatic shellstructure through comer parts thereof will be explained.

The sheet layers of a pneumatic shell structure are always placed undera stressed condition because of the internal pressure due to aircontained in the airtight chamber. This stressed condition is variablefollowing the variation of the internal pressure and the corner partsare liable to be accompanied with creases made thereon due to thevariation in the stressed condition. Such crease formation often causesaccidental seeping of water into the shell structure. In order toeliminate this trouble, the present invention provides the followingcorner part sealing system.

As is shown in FIG. 19, the corner part of a pneumatic shell structureis classified into a projecting corner 71 and a receding corner 72. Inthe ensuing description, a sealing system for the comer of the formertype will be explained as an example. Referring to FIG. 20, in fixingthe sheet layer 2 composed of the upper sheet layer 4 and lower sheetlayer 5 on the supporting member 31, a corner part of the sheet layersuperimposed on the corner part 71 is previously cut off as is shown inFIG. 21A. Aside from this, a corner sealing member 73 having aconfiguration as shown in FIG. 21B is previously prepared. Generally,the corner sealing member 73 is made of a synthetic resin film the sameas that used for making the sheet layer 4. However, it can be made ofother materials such as metal plate, plastic plate or reinforced plasticplate containing glass fibers. After preparation of the comer sealingmember 73, it is placed on the lower sheet layer and is adhered thereonby an adhesive layer 74 in a watertight condition as shown in FIG. 21C.Next, the upper sheet layer 4 is placed on thus adhered corner sealingmember 73 and is adhered tetrahydroxybenzophenone,2-hydroxy-4,4'-dimethoxybenzophenone, 2,4-dihydroxybenzophenone,2-hydroxy-4- methoxybenzophenone, 2,2-dihydroxybenzophenone, 2,2-dihydroxy-4,4-diethoxybenzophenone, and 2-hydroxy-4-octhereon by anadhesive layer 75 in a watertight condition as 5 toxybenzophenone, andtriazols such as O-hydroxyphenyl shown n HQ Z Thus, the Corner Parts Ofthe Pheumatle triazol. For the purpose of protecting the shell structurefrom h ll Structure Can be Provided With complete watertight Pundesirable influences of heat, it is recommended to cover the p ytogether With refihed appearance when the Pneumatic synthetic resin filmespecially polyethylene terephthalate film, shell structure of thepresent invention is adapted for out-door i h a metal layer tt d b vauum eva oration which has it is subjected to xp to sun-light h n, h athickness of m or thinner. This sputtered metal layer synt r n m c p ngh h l Structure are should be placed beneath the above-describedultraviolet ray degraded owing to heat and ultraviolet rays from thesun-light intercepting layer. If the thickness of the metallic layerexand the heat come in hrough the Sh layers r lting in ceeds 20 mp, ittends to undesirably intercept even the visible elevation of theinternal temperature. In order to eliminate 15 light rays. Such kind ofmetals as aluminum, silver, zinc and these troubles, the art of thepresent invention proposes provio er can be used for this purpose in anyof the known sion of a heat-insulation layer and/or an ultraviolet rayintervacuum evaporation manners. cepting layer to the outside layer orlayers. It is already known By disposing the heat intercepting layer ofthis nature that a resistance ofthe layer against weather conditions canbe together with the u t a o et ray intercepting layer onto the enhancedby mixing or coating a suitable ultraviolet ray absor- 2O outermostPonioh of the Sheet y n y the Visible light can bent to the syntheticresin film in the manufacturing thereof. p through the layers Wltheffective ehmmauoh of l lln the conventional weather-resisting sheetlayer, a weathertravlolet'rayS! near Infrared y and Infrared Y containedproofing film of a desired thickness or a plurality of superimthesuh'hght- I posed weather-proofing films are used for preparing the ThePheumauc h?" structlh'e the Present 'h desired thickness and themanufacturing cost thereof is very composed of belt'hke synthetlc reismfilms supenmposfad to expensive. Facing this trouble, a modifiedembodiment of the each other by a novel construcung by W h a pneumaticshell structure of the present invention comprises stlrongly consqgctedf g z i E be obtained m a an additional synthetic resin protector filmcovering the ordip W PP era y owere costs nary synthetic resin filmlayers. The thickness of the additional a we 6 3 l. A pneumatic shellstructure comprising first and second protector film is 25 1, or th1nnerand the protector is capable of sheet means of air and water impermeablematerlal; means for absorbing and/or intercepting ultraviolet rayshav1ng a wave hermet1cally sealing said first and second sheet meanslength of 350 mp, or shorter. Polyethylene terephthalate film 1s h d h hh favorabl used for this u ose This 01 eth lene tere hthatoget er amun tpenp enes to prov] e an almgt 1 fl y h f p p chamber between sa1d firstand second sheet means; each said ate o SOT mg g gf g l sheet meansincluding an outer layer, an airtight inner layer Wave eng 5 or S an y Wt ls defining a portion of said airtight chamber, and an interdegraded'If Several Sheets 0 p9lyethy tereph mediate layer disposed between saidinner and outer layers, films are exposed to ultravlolet rays asupenmposed f said intermediate layer comprising a plurality of firststrips of only ofnermost film degraded by h ultravlolet synthetic resinfilm having longitudinal and transverse extents y and the Inside filmSheets are, to an appfeclable f f 40 defining major surfaces thereof,said strips being arranged in a prevented from degradation, by the rays.This protect1on 1s configuration wherein they are disposed in paralleland due f the Putermost ph y y threphthalatef film being cessivelyshifted in the direction of said transverse extents so Provlded W1th thefuhfmoh of absorblhg and/Or lhtel'cephhg that a longitudinal marginalsurface portion of each said strip the uhfavlolet y hav1ng a wave lengthof 350 "h foverlaps a longitudinal marginal surface portion of the nextRefemhg to Table wealher'proof of the Supenmposed succeeding strip andis unattached thereto along said longitu- OUS kinds of synthetic resinfilms are Showhdinal marginal surface portion; and support meansconnected TABLE .2

Exposed to sunlight Unexposed 6 months 12 months Tensile BreakingTensile Breaking Tensile Breaking strength elongation strengthelongation strength elongation Sprcillltn Film Lnyvr (kg/mm?) (percent)(kg/mm?) (percent) (kg/mm?) (percent) l'olyvinyl chloride 1 1 277 1.5 413s 0 n llllll of 351.1 thhk- I l. 7 (l 0 noss'. l L 1.6 1) (I ll.lolyntllylunn toropln l i227 l. U (l (l t) thnlntu Iilnl M251; 2 12718.15 103 16. 4 .18 thickness. 1 I: 2131.1; {ill 2 n. 0 .1) 2 1n z 12021. 4 121 20.1 116 3 126 21, s 123 20. 7 120 *Weatherproof polyethyleneterephthalate Iil1n containing 0.3% of 2-l1ydroxy-4-oct0xybenzophenone.

As shown in Table 2, the degrading rate of the polyvinylchloride filmspecimen A is almost similar to the layers from 1 to 3 whereas, in caseof the film specimen B, the degrading rates of the 2nd and 3rd layer isconsiderably smaller than that of the 1st layer. In the case of filmspecimen C, the 1st film layer contains an ultraviolet ray absorbant, 2-

to said hermetically sealed peripheries of said first and second sheetmeans.

2. A pneumatic shell structure as set forth in claim 1, furthercomprising means for hermetically sealing said connection between saidsupport means and said peripheries of said first and second sheet means.

3. A pneumatic shell structure as set forth in claim 1, in which saidfirst strips of synthetic film are made of polyethylene terephthalateresin.

4. A pneumatic shell structure as set forth in claim 1, in which saidouter layer of each said sheet means comprises a plurality of secondstrips of synthetic resin film having longitudinal and transverseextents defining major surfaces thereof,

said second strips being arranged in a configuration which is the sameas said configuration of said first strips.

5. A pneumatic shell structure as set forth in claim 4, in which saidsecond strips of synthetic film are made of polyethylene terephthalateresin.

6. A pneumatic shell structure as set forth in claim 5, in which saidoverlapping marginal surface portions of said second strips arehermetically sealed together.

7. A pneumatic shell structure as set forth in claim 1, in which saidinner layer of each said sheet means comprises a plurality of thirdstrips of synthetic resin film having longitudinal and transverseextents defining major surfaces thereof, said third strips beingarranged in a configuration which is the same as said configuration ofsaid first strips, and in which said overlapping marginal surfaceportions of said third strips are hermetically sealed together.

8. A pneumatic shell structure as set forth in claim 7, in which saidthird strips of synthetic film are made of polyethylene terephthalateresin.

9. A pneumatic shell as set forth in claim 1, further comprisingreinforcing means including a synthetic resin film received within saidairtight chamber and connected to said first sheet means, said filmextending toward said second sheet means in a substantiallyperpendicular relationship with said first and second sheet means.

10. A pneumatic shell structure as set forth in claim 1, in which saidsupport means is coated with a paint membrane having a pencil hardnessof at least F degree and a Sward Riickers hardness value of at least 25,and further comprising means for hermetically sealing said connectionbetween said support means and said peripheries of said first and secondsheet means.

11. A pneumatic shell structure as set forth in claim 1, in which saidshell structure has a corner portion and further comprising a comersealing member hemetically sealed to said corner portion.

12. A pneumatic shell structure as set forth in claim 1, in which saidfirst sheet means includes at least one film layer containing anultraviolet ray absorbing agent means.

13. A pneumatic shell structure as set forth in claim 12, in which saidfilm layer is a synthetic resin film of polyethylene terephthalate, andin which said absorbing agent means is for absorption of ultravioletrays having wave lengths of at most 350 m 14. A pneumatic shellstructure as set forth in claim 1, further comprising a sputtered metalcoating on said outer layer.

15. A pneumatic shell structure as set forth in claim 14, furthercomprising an ultraviolet absorption coating on said sputtered metalcoating.

16. A pneumatic shell structure as set forth in claim 14, in which saidouter layer is a polyethylene terephthalate film.

17. A pneumatic shell structure as set forth in claim 1, furthercomprising ventilating means disposed within at least one of said firstand second sheet means for venting air contained within said one sheetmeans to the atmosphere.

18. A pneumatic shell structure as set forth in claim 17, in which saidouter layer of each said sheet means comprises a plurality of secondstrips of synthetic resin film having longitudinal and transverseextents defining major surfaces thereof, said second strips beingarranged in a configuration which is the same as said configuration ofsaid first strips, and in which said ventilating means comprises a pipeinserted between said overlapping marginal surface portions of two ofsaid second strips.

19. A pneumatic shell structure as set forth in claim 17, in which saidventilating means comprises a pipe inserted between said outer andintermediate layers at said periphery of said one sheet means.

2. A pneumatic shell structure as set forth in claim 1, furthercomprising means for hermetically sealing said connection between saidsupport means and said peripheries of said first and second sheet means.3. A pneumatic shell structure as set forth in claim 1, in which saidfirst strips of synthetic film are made of polyethylene terephthalateresin.
 4. A pneumatic shell structure as set forth in claim 1, in whichsaid outer layer of each said sheet means comprises a plurality ofsecond strips of synthetic resin film having longitudinal and transverseextents defining major surfaces thereof, said second strips beingarranged in a configuration which is the same as said configuration ofsaid first strips.
 5. A pneumatic shell structure as set forth in claim4, in which said second strips of synthetic film are made ofpolyethylene terephthalate resin.
 6. A pneumatic shell structure as setforth in claim 5, in which said overlapping marginal surface portions ofsaid second strips are hermetically sealed together.
 7. A pneumaticshell structure as set forth in claim 1, in which said inner layer ofeach said sheet means comprises a plurality of third strips of syntheticresin film having longitudinal and transverse extents defining majorsurfaces thereof, said third strips being arranged in a configurationwhich is the same as said configuration of said first strips, and inwhich said overlapping marginal surface portions of said third stripsare hermetically sealed together.
 8. A pneumatic shell structure as setforth in claim 7, in which said third strips of synthetic film are madeof polyethylene terephthalate resin.
 9. A pneumatic shell as set forthin claim 1, further comprising reinforcing means including a syntheticresin film received within said airtight chamber and connected to saidfirst sheet means, said film extending toward said second sheet means ina substantially perpendicular relationship with said first and secondsheet means.
 10. A pneumatic shell structure as set forth in claim 1, inwhich said support means is coated with a paint membrane having a pencilhardness of at least F degree and a Sward Rucker''s hardness value of atleast 25, and further comprising means for hermetically sealing saidconnection between said support means and said peripheries of said firstand second sheet means.
 11. A pneumatic shell structure as set forth inclaim 1, in which said shell structure has a corner portion and furthercomprising a corner sealing member hemetically sealed to said cornerportion.
 12. A pneumatic shell structure as set forth in claim 1, inwhich said first sheet means includes at least one film layer containingan ultraviolet ray absorbing agent means.
 13. A pneumatic shellstructure as set forth in claim 12, in which said film layer is asynthetic resin film of polyethylene terephthalate, and in which saidabsorbing agent means is for absorption of ultraviolet rays having wavelengths of at most 350 m Mu .
 14. A pneumatic shell structure as setforth in claim 1, further comprising a sputtered metal coating on saidouter layer.
 15. A pneumatic shell structure as set forth in claim 14,further comprising an ultraviolet absorption coating on said sputteredmetal coating.
 16. A pneumatic shell structure as set forth in claim 14,in which said outer layer is a polyethylene terephthalate film.
 17. Apneumatic shell structure as set forth in claim 1, further comprisingventilating means disposed within at least one of said first and secondsheet means for venting air contained within said one sheet means to theatmosphere.
 18. A pneumatic shell structure as set forth in claim 17, inwhich said outer layer of each said sheet means comprises a plurality ofsecond strips of synthetic resin film having longitudinal and transverseextents defining major surfaces thereof, said second strips beingarranged in a configuration which is the same as said configuration ofsaid first strips, and in which said ventilating means comprises a pipeinserted between said overlapping marginal surface portions of two ofsaid second strips.
 19. A pneumatic shell structure as set forth inclaim 17, in which said ventilating means comprises a pipe insertedbetween said outer and intermediate layers at said periphery of said onesheet means.